Comstock/Thinkstock(TEMPE, Ariz.) -- Nearly three years after 8-month-old Gabriel Johnson was reported missing in San Antonio, Texas, prosecutors say his mother used him as a pawn against his biological father because she was angry at him and wanted to hurt him in the aftermath of their relationship.

Closing arguments were heard on Tuesday in the trial of baby Gabriel's mother, Elizabeth Johnson, 26, in Superior Court of Maricopa County in Arizona. Johnson has pleaded not guilty to charges of kidnapping, custodial interference and conspiracy in the December 2009 disappearance of her son.

Johnson had been embroiled in a custody battle with Gabriel's biological father, Logan McQueary. Johnson had wanted to put their son up for adoption, but McQueary did not.

While she was fighting with McQueary over custody of their son, Johnson left Tempe, Ariz., with Gabriel and traveled to San Antonio, Texas, on Dec. 18, 2009. Johnson failed to bring Gabriel back to visit with McQueary two days later, violating a court custody order.

Gabriel was last seen with his mother on Dec. 26, 2009. The following day, Johnson sent text messages to McQueary saying she had killed him.

Johnson listened tearfully in court as prosecutor Angela Andrews read portions of the transcript of the recorded conversation Johnson had with McQueary after she told him she killed Gabriel.

Johnson was recorded telling McQueary that she suffocated their son with a towel until he turned blue. She said she then put his body in a diaper bag and put the bag in the trash.

Later, Johnson told authorities she gave Gabriel to a couple she met in a park in San Antonio.

In his closing statements, Johnson's attorney, Marc Victor, said he disagrees that what Johnson did could be characterized as kidnapping.

Victor said he did not call witnesses because the state did not present a convincing case that Johnson was guilty of kidnapping. He instead said the lawsuit was an example of "an ugly custody interference case."